As is known in the art, transducers are used in a variety of applications to convert energy from one form to another. For example, in acoustic transmitter applications (e.g., loudspeaker applications), transducers typically convert electrical energy into acoustic energy and transmit or emit the converted acoustic energy. Additionally, in acoustic sensing applications (e.g., microphone applications), transducers typically convert sensed or detected acoustic energy into electrical energy. Ultrasonic transducers are one example type of transducer which may convert electrical energy to acoustic energy, particularly high frequency acoustic energy (e.g., acoustic energy having a frequency of greater than about twenty kilohertz (kHz)). Ultrasonic transducers may transmit the converted acoustic energy (e.g., at a transducer output). Additionally, ultrasonic transducers may convert sensed or detected high frequency acoustic energy to electrical energy.
Conventional ultrasonic transducers generally comprise one or more piezoelectric elements which are provided from piezoelectric materials (e.g., piezoelectric ceramics, crystals, composites and/or polymers), and use the piezoelectric effect to emit or detect high frequency acoustic energy. For example, electrical stimulation of the piezoelectric materials in the piezoelectric elements may cause mechanical distortion of the piezoelectric materials, resulting in vibrations of the materials and production of acoustic energy by the piezoelectric elements and, thus, the ultrasonic emission.
While conventional piezoelectric ultrasonic transducers are capable of emitting and/or detecting high frequency acoustic energy, they are subject to several drawbacks. One example drawback is that the piezoelectric elements found in conventional piezoelectric ultrasonic transducers are typically only capable of generating acoustic energy having a single frequency. As a result of the foregoing, in applications where broadband frequency coverage is required, conventional piezoelectric ultrasonic transducers generally comprise large arrays of piezoelectric elements, making piezoelectric ultrasonic transducers costly and unsuitable for compact applications (e.g., mobile communications systems).